sdp_msg: when NULL, do not crash but return empty SDP str

Change-Id: Ibd5c43fae61cd006d8fb42a06b99a609356f7037
---
M src/libmsc/sdp_msg.c
1 file changed, 10 insertions(+), 2 deletions(-)


git pull ssh://gerrit.osmocom.org:29418/osmo-msc refs/changes/06/30106/1

diff --git a/src/libmsc/sdp_msg.c b/src/libmsc/sdp_msg.c
index eda6ac9..09e1277 100644
--- a/src/libmsc/sdp_msg.c
+++ b/src/libmsc/sdp_msg.c
@@ -220,8 +220,16 @@
 {
 	const struct sdp_audio_codec *codec;
 	struct osmo_strbuf sb = { .buf = dst, .len = dst_size };
-	const char *ip = sdp->rtp.ip[0] ? sdp->rtp.ip : "0.0.0.0";
-	char ipv = osmo_ip_str_type(ip) == AF_INET6 ? '6' : '4';
+	const char *ip;
+	char ipv;
+
+	if (!sdp) {
+		OSMO_STRBUF_PRINTF(sb, "%s", "");
+		return sb.chars_needed;
+	}
+
+	ip = sdp->rtp.ip[0] ? sdp->rtp.ip : "0.0.0.0";
+	ipv = (osmo_ip_str_type(ip) == AF_INET6) ? '6' : '4';
 
 	OSMO_STRBUF_PRINTF(sb,
 			   "v=0\r\n"

